Face seals have been used to eliminate leakage that often arises from improper use or other deficiencies of fittings that rely on metal-to-metal sealing. A typical face seal fitting includes a fitting body having a center bore that opens to a transverse sealing face. The outer periphery of the fitting body often is provided with external threads while the sealing face has formed therein an annular groove for containing an annular seal. The annular seal usually has an axial dimension greater than the depth of the groove so as to project from the sealing face. Accordingly, the annular seal will be compressed in the groove upon being engaged by a confronting sealing surface of a mating part.
Face seals are commonly used in various types of valves in applications for controlling and directing the flow of liquids or gases from one or more inlet ports to a common outlet port. Such valves are commonly constructed with an axially movable poppet located inside a valve body with a cylindrical bore. A biasing shaft is connected to the poppet to transmit a bias force to the poppet. Common methods for applying the bias force to the shaft include springs, pneumatic or hydraulic cylinders, and solenoid coils.
Elastomeric and thermoplastic materials have been found to be suitable seal materials for both low and high fluid pressure applications, including those in the dirty valve applications, such as in the energy, oil, and gas industries. While elastomeric valve seats are adequate for many applications, they may be less resistant to abrasion than thermoplastic materials and thus more prone to damage from contaminants in the fluids and wear from repeated valve cycling. Elastomeric materials may also be more likely than thermoplastic materials to suffer from degradation caused by chemical attack or extreme low or high temperatures. On the other hand, thermoplastic materials may be less resilient than elastomeric materials, which can make them less suitable for proving a reliable dynamic seal. In either case, when used in high pressure dirty valve applications, debris can break down the seal over time.
Thus, while material selection may be useful in improving the performance and durability of seals in certain applications, it is desirable to improve the functionality of face seal assemblies without modifying the seal material.